The diamond coating of sharpening and cutting tools is known. These tools include saw blades for cutting masonry, files of many sizes and shapes used in pattern-making and machining, and honing stones which can vary in size from small pocket size for sharpening points on articles such as fish hooks to much larger honing stones for honing planer blades etc. Known sharpening tools may be made of plastic with the diamond rolled into the surface. Other sharpening tools have the diamond surface formed on an alloy base which is usually relatively thin and mounted onto a timber block for support. These known sharpening tools lack the strength and rigidity necessary for accurate grinding operations. It is sometimes necessary for tools such as drill and router bits to be reshaped by a grinding operation prior to being edge-sharpened by honing. Known sharpening tools are mostly ineffective for both grinding and honing.
Some router bits have concave cutting faces and are difficult to sharpen with a flat or straight edged stone which cannot reach into the concavity of the cutting face. Furthermore known sharpening tools are mostly inadequate for sharpening the bottom or plunging edge of a router cutter.
My Australian application no. 55928/90 addresses these problems and provides a sharpening device having an elongated mounting shaft and a disk-like sharpening head integral therewith at one end thereof, the distal surface of the sharpening head being coated with a fine layer of diamond particles to form a sharpening face. The tool is effective in overcoming many of the disadvantages outlined above but still has a number of disadvantages.
In particular, it has been found that when grinding with the sharpening device held in a drill positioned downwardly, it is difficult to ensure that lubricating fluid lubricates the workpiece which is obscured by the sharpening head. In use, as the sharpening device rotates, the lubricating fluid is spun outwardly over the substantially horizontal upper surface of the disc-like sharpening head and is flung off at the unction of the upper surface and the edge of the sharpening head. Furthermore because the edge portion of the disc-like sharpening head is relatively thick, the sharpening face is unable to enter a surface having a low or angled overhang and accordingly router bits having such surfaces cannot be effectively sharpened with the sharpening device of 55928/90.
The present invention aims to alleviate the above disadvantages and to provide a support assembly which will be reliable and efficient in use. Other objects and advantages of this invention will hereinafter become apparent.